The study "Vulnerability Markers in Prodromal Schizophrenia" will identify, assess and follow individuals at high risk for schizophrenia (at-risk group) who will be compared to normal subjects using 1) clinical assessment 2) psychophysiological and 3) neuropsychological measures of information processing. The specific aims of the study are to better understand pre-psychotic symptomatology and the predictive profile of prodromal signs and symptoms of schizophrenia through longitudinal clinical assessment and to determine whether at-risk subjects have information processing deficits consistent with those observed in other schizophrenic spectrum populations. Increased knowledge regarding the onset of psychosis may help to better identify individuals who are at-risk for psychosis and provide insight into the neurodevelopmental processes that occur in this stage. The first hypothesis of the proposed study is that the at-risk group will have abnormalities of information processing when compared to normals. In this context, it is predicted that the at-risk group will have decreased prepulse inhibition and habituation of the startle response; impaired visual backward masking; reduced P50 event related potential gating; and neuropsychological deficits. The second hypothesis states that information processing performance will be reliable across repeated test sessions that will occur over a 2 year period, suggesting that the information processing measures are stable measures of trait-related deficits. The third hypothesis states that the clinical and information processing measures will be differentially correlated with each other and one or more factors will predict which individuals will make the transition to psychosis. If neurobiological markers can be identified that are predictive of later psychosis, these markers could be used in conjunction with clinical assessment in determining which subjects would benefit from early treatment. Appropriate intervention at this early stage could possible thwart the development of a psychotic illness along with associated difficulties and deterioration. Delaying the emergence of psychosis may in itself be beneficial because a more mature individual may be better able to deal with the onset of a psychotic illness. The disruption of social networks, education and occupational activity as well as the high incidence of suicide and crime that often accompany psychosis might be reduced or averted.